Evidence in favour of an underlying cholinergic degeneration in PD psychosis among cognitively impaired patients has been supported by the fact that choline acetyl transferase reduction has been found in the neocortex of hallucinating PD as well as Lewy body dementia patients [103, 104] and the fact that cholinesterase inhibitors improve psychotic symptoms in some cases of Lewy body dementia patients [105, 106]. The gene discussed is BCHE; the disease is psychotic disorder.